.TH RADRELAY 8 "23 October 2007" "" "FreeRADIUS Daemon"
.SH NAME
radrelay -- Deprecated command.
.SH DESCRIPTION
The functions of \fIradrelay\fP have been added to \fIradiusd\fP.  One
benefit is that one instance of \fIradiusd\fP can read multiple detail
files, among others.
.PP
The \fIrlm_sql_log\fP module does something similar, but for SQL
queries.  See it's man page for details.
.SH "REPLICATION FOR BACKUPS"
Many sites run multiple radius servers; at least one primary and one
backup server. When the primary goes down, most NASes detect that and
switch to the backup server.

That will cause your accounting packets to go the the backup server -
and some NASes don't even switch back to the primary server when it
comes back up.

The result is that accounting records are missed, and/or the
administrator must jump through hoops in order to combine the
different detail files from multiple servers. It also means that the
session database ("radutmp", used for radwho and simultaneous use
detection) gets out of sync.

We solve this issue by "relaying" packets from one server to
another, so they both have the same set of accounting data.

See raddb/sites-available/buffered-sql for more information.
.SH "BUFFERING FOR HIGH-LOAD SERVERS"
If the RADIUS server suddenly receives a many accounting packets,
there may be insufficient CPU power to process them all in a timely
manner.  This problem is especially noticable when the accounting
packets are going to a back-end database.

Similarly, you may have one database that tracks "live" sessions, and
another that tracks historical accounting data.  In that case,
accessing the first database is fast, as it is small.  Accessing the
second database many be slower, as it may contain multiple gigabytes
of data.  In addition, writing to the first database in a timely
manner is important, while data may be written to the second database
with a few minutes delay, without any harm being done.

See raddb/sites-available/copy-to-home-server for more information.
.SH SEE ALSO
.BR radiusd(8),
.BR rlm_sql_log(5)
.SH AUTHOR
The FreeRADIUS Server Project
